CN117340041A

CN117340041A - Bimetal composite pipe and preparation method thereof

Info

Publication number: CN117340041A
Application number: CN202311286953.4A
Authority: CN
Inventors: 赵映辉; 何航; 宋光鑫; 张敏; 赵健明; 朱林; 肖松良; 李飞; 卓钊; 周正平; 沈枫林
Original assignee: Hengyang Valin Steel Tube Co Ltd
Current assignee: Hengyang Valin Steel Tube Co Ltd
Priority date: 2023-10-07
Filing date: 2023-10-07
Publication date: 2024-01-05

Abstract

The invention provides a bimetal composite pipe and a preparation method thereof. The preparation method comprises the following steps: preparing a tube blank: taking a square tube as an outer layer square tube and a round tube as an inner layer round tube; and (3) assembling: sleeving the outer square tube on the periphery of the inner circular tube, inserting a core rod into the inner circular tube, and inserting an exhaust tube into a gap between the R angle of the outer square tube and the inner circular tube to obtain a fitting tube; pre-heading: pre-heading the assembled pipe to obtain an inner pipe bottle blank and an outer pipe bottle blank with a core rod; periodically rolling a pipe: and (5) performing periodic tube rolling on the inner and outer tube bottle blanks to obtain a composite tube blank. The preparation method of the technical scheme can solve the problem that the inner pipe and the outer pipe of the existing bimetal composite pipe are easy to move.

Description

Bimetal composite pipe and preparation method thereof

Technical Field

The invention relates to the technical field of composite tube manufacturing, in particular to a bimetal composite tube and a manufacturing method thereof.

Background

Corrosion is a serious problem throughout the use of steel pipes, which inevitably encounter H-containing products ₂ S、CO ₂ And Cl ions, which are very corrosive to the tubing, not only cause great economic loss, but also often bring about catastrophic results in terms of environmental and personnel safety. Generally, low-cost carbon or low-alloy steel pipes have poor corrosion resistance, and stainless steel, nickel-based alloy and other materials with good corrosion resistance have high price. To save the amount of expensive materials, bimetallic composite tubes have been developed. The bimetal composite pipe is generally composed of an outer base pipe with strength and a corrosion-resistant lining pipe, has no difference from the corrosion-resistant alloy pipe in corrosion resistance, is superior to a carbon steel pipe and a common alloy pipe in strength, has the price about half of that of the corrosion-resistant alloy pipe, and has the service life far longer than that of the carbon steel pipe. The bimetal composite pipe integrates comprehensive performances such as strength, corrosion resistance, wear resistance, high pressure resistance, economy and the like, is widely applied to oil and gas exploitation and transportation, ocean engineering, power industry, water supply engineering and the like, has wide specification coverage range, and has been increasingly applied in various industries in recent years due to the consideration of deterioration of service environment (high temperature, high pressure, high corrosion and the like) and cost.

In the prior art known by the inventor, the inner and outer tubes of the bimetal composite tube are round tubes, and when the bimetal composite tube is assembled, because gaps are formed between the outer periphery of the inner tube and the inner periphery of the outer tube, and the gaps between the inner tube and the outer tube are generally large in order to facilitate the outer tube to be sleeved on the outer periphery of the inner tube, the inner tube and the outer tube are easy to move.

Disclosure of Invention

The invention mainly aims to provide a bimetal composite pipe and a preparation method thereof, which can solve the problem that the inner pipe and the outer pipe of the existing bimetal composite pipe are easy to move, ensure the integrity of a composite interface and effectively improve the quality of the composite pipe.

In order to achieve the above object, according to an aspect of the present invention, there is provided a method for manufacturing a bimetal composite pipe, comprising the steps of: preparing a tube blank: taking a square tube as an outer layer square tube and a round tube as an inner layer round tube; and (3) assembling: sleeving the outer square tube on the periphery of the inner circular tube, inserting a core rod into the inner circular tube, and inserting an exhaust tube into a gap between the R angle of the outer square tube and the inner circular tube to obtain a fitting tube; pre-heading: pre-heading the assembled pipe to obtain an inner pipe bottle blank and an outer pipe bottle blank with a core rod; periodically rolling a pipe: and (5) performing periodic tube rolling on the inner and outer tube bottle blanks to obtain a composite tube blank.

Further, the outer diameter of the inner round tube is 5 mm-10 mm smaller than the diameter of the inscribed circle of the outer square tube.

Further, the side length of the outer square tube is A, the side concave-convex degree is less than or equal to 0.2 percent A, the wall thickness of the corner radius is 1.5 times to 3 times, the side verticality is 90 degrees+/-0.3 degrees, and the outer diameter of the round tube is 5mm to 10mm smaller than the minimum inner diameter of the square tube.

Further, in the assembling step, the outer square tube and the inner circular tube of the assembling pipe are axially staggered by a distance of 2 mm-5 mm.

Further, in the step of pre-priming, the step of performing pre-priming includes: the assembly pipe is placed on a heading machine, a first heading module and a second heading module of the heading machine are pressed down, then the first heading module and the second heading module are lifted, the assembly pipe is rotated by 90 degrees, the first heading module and the second heading module are pressed down again, an inner pipe bottle blank and an outer pipe bottle blank are obtained, and vacuumizing and sealing treatment are carried out from an exhaust pipe.

Further, in the pre-heading step, the hole pattern of the first heading module and the hole pattern of the second heading module are formed by three sections of oblique lines, the sum of the hole pattern widths of the first section and the first heading module of the second section is 300mm, the sum of the hole pattern widths of the first section and the second heading module of the second section is 300mm, the width range of the first section of the first heading module is 218 mm-235 mm, the included angle with the horizontal line is 16.8-28 °, the width range of the second section of the first heading module is 65 mm-82 mm, the included angle with the horizontal line is 6-10 °, the width range of the third section of the first heading module is 28 mm-145 mm, the included angle with the horizontal line is 46-52 °, the width range of the first section of the second heading module is 218 mm-235 mm, the included angle with the horizontal line is 16.8-28 °, the width range of the second section of the second heading module is 65 mm-82 mm, the included angle with the horizontal line is 6-10 °, the width range of the third section of the second heading module is 4-32 ° and the included angle with the horizontal line is 78 °.

Further, the outer diameter of the composite tube blank obtained by periodically rolling the tube is 150-600 mm, the included angle between the first end of the composite tube blank and the horizontal line is 46-52 degrees, the included angle between the second end of the composite tube blank and the horizontal line is 78-83 degrees, and the ratio of the wall thickness of the outer square tube to the wall thickness of the inner circular tube of the composite tube blank is 1:1.25-6:1.

Further, the step of periodically rolling the tube includes: and (3) periodically rolling the inner and outer tube blanks by using a periodical tube mill group to obtain a composite tube blank, setting the hole pattern of the periodical tube mill group to be phi 150-phi 600mm, determining curve equations of the forging and rolling section, the finishing and rolling section and the blank rolling section by using the hole pattern comprising the forging and rolling section, the finishing and rolling section and the blank rolling section, wherein the forging and rolling section is an envelope curve, the initial angle of the forging and rolling section is 27-30 degrees, the included angle is 74-84 degrees and the curve expansion length is 200-600 mm, and controlling the roller rotating speed of the periodical tube mill group to be 46-72 rpm and the wind pressure to be 3-4 bar.

Further, after the step of periodically rolling the tube, the step of heating is further included: preheating the composite tube blank, wherein the preheating temperature is less than or equal to 620 ℃, soaking the composite tube blank, the soaking temperature is 1210-1240 ℃, and the sum of the preheating time and the soaking time is 2.5-16 h.

Further, after the heating step, the method further comprises the step of head-aligned perforation: and (3) perforating the heated composite tube blank by using a perforating machine to obtain a blank tube, wherein the outer square tube of the blank tube is flush with the tube section of the inner circular tube, the total diameter reduction rate of the perforating machine is 16-18%, the ovality is 1.02 and the expansion rate is 5-20%.

Further, after the step of the blind end piercing, the method further comprises the step of rolling: rolling the hollow billet to obtain the composite hollow billet.

Further, after the step of rolling, the step of reheating is further included: reheating the composite pierced billet by a step furnace, wherein the furnace feeding temperature is lower than 450 ℃, the solid solution strengthening heating temperature of the step furnace is 1000+/-10 ℃, and the heat preservation time is 0.5-4 h.

Further, after the reheating step, the sizing step is further included: sizing the reheated composite pierced billet by a sizing mill and a cooling water ring on the sizing mill to obtain a composite pipe, cooling the composite pipe by a cooling water ring group to obtain a bimetal composite pipe, wherein the temperature of the composite pierced billet entering the sizing mill is 940-980 ℃, the temperature of the composite pierced billet exiting the sizing mill is 680-720 ℃, when the composite pierced billet enters the cooling water ring group, the temperature of cooling water of the cooling water ring group is 670-710 ℃, and when the composite pierced billet exits the cooling water ring group, the temperature of cooling water of the cooling water ring group is 380-420 ℃.

In order to achieve the above object, according to another aspect of the present invention, there is provided a bimetal composite pipe manufactured using the above manufacturing method.

By adopting the technical scheme of the invention, the combination of the outer layer square tube and the inner layer square tube is adopted, after the outer layer square tube is sleeved on the periphery of the inner layer square tube, the inner wall of the inner layer square tube and the inner wall of the outer layer square tube are provided with near tangent parts, in the parts, the gap between the inner layer square tube and the outer layer square tube is smaller, the inner layer square tube can be contacted with the outer layer square tube by moving a short distance along the radial direction, the friction force between the inner layer square tube and the outer layer square tube can be generated, the moving distance of the inner layer square tube relative to the outer layer square tube can be reduced to a certain extent, and when the minimum gap between the inner layer square tube and the outer layer square tube is very small, the moving between the inner layer square tube and the outer layer square tube can be avoided.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:

FIG. 1 shows a flow chart of a method of preparation of an embodiment of the invention;

FIG. 2 shows a longitudinal cross-sectional view of an embodiment of the present invention with an outer square tube around the circumference of a thin-walled inner round tube;

FIG. 3 is a longitudinal sectional view showing the outer layer round tube of the comparative example of the present invention after being sleeved on the outer periphery of the thick-wall inner layer round tube;

FIG. 4 shows a cross-sectional view of an inner and outer tube preform of an embodiment of the present invention;

FIG. 5 shows a cross-sectional view of a composite pipe blank according to an embodiment of the invention;

FIG. 6 shows a cross-section of the head of an inner and outer tube preform of an embodiment of the present invention;

FIG. 7 shows a schematic diagram of the step of flush perforation of an embodiment of the present invention;

FIG. 8 illustrates a schematic diagram of the steps of periodic tube bundling of an embodiment of the present invention;

fig. 9 is a schematic structural view showing a mandrel mill according to an embodiment of the present invention.

Wherein the above figures include the following reference numerals:

1. square tubes; 2. a round tube; 3. a heading module; 4. b, punching the head; 5. and (5) connecting a pipe mill.

Detailed Description

It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other. The invention will be described in detail below with reference to the drawings in connection with embodiments.

In the prior art known to the inventors, there are five commonly used methods for preparing a bimetal composite pipe, which are respectively: mechanical rolling, explosion compounding, drawing compounding, hydraulic compounding and explosion compounding plus hot rolling compounding.

The mechanical spinning method uses the mechanical properties of two different materials, namely, the elastic deformation range of an outer base pipe (carbon steel pipe) and the characteristic of low yield strength of an inner liner pipe (stainless steel pipe). Under the extrusion of screw feeding of the rolling machine, the lining pipe is continuously and locally plastically deformed, and the outer base pipe is always kept within the elastic deformation range. When the external force is removed, the outer base pipe elastically contracts, and the lining pipe cannot contract due to plastic deformation. Thereby the inner lining pipe outer surface is strongly embedded in the inner surface of the outer base pipe to be compositely formed.

The explosion compounding method is that the assembled inner and outer pipes are placed in a water tank, the cluster explosive is placed on the axis of the inner liner pipe, the water pressure in the water tank is increased instantaneously by the explosive force produced instantaneously by the explosive, the instantaneously increased water pressure pushes the inner liner pipe to expand outwards in the diameter direction in the instantaneously, the outwards expanded inner liner pipe expands on the inner surface of the outer base pipe under the action of the water pressure, and the expansion is continued along with the outer base pipe under the action of the water pressure until the pressure disappears; and the outer base pipe is contracted inwards in the axial direction, and finally the composite forming is carried out.

The hydraulic compounding process is to seal the assembled inner pipe and outer pipe inside the sealed long pipe completely, inject liquid into the pipe, pressurize the liquid inside the pipe gradually to expand the lining pipe gradually and shrink the lining pipe inwards in the axial direction. The lining pipe finally achieves plastic deformation through continuous gradual pressure application, the outer base pipe is still in the elastic deformation range, and when the inner pipe and the outer pipe are judged to achieve plastic deformation through the pressure gauge, the pressure is applied when the outer base pipe is in the elastic deformation requirement, and the lining pipe is in a composite mode.

The drawing compounding method is to draw the assembled inner and outer tubes along the axis of the lining tube through a die with a taper (usually the taper is 1:25 and 1:50) and a fixed size of the largest outline outer circle. The lining pipe is compounded on the inner surface of the outer base pipe in the diameter direction by means of extrusion and expansion of a drawing die, and the outer base pipe is also in the range of elastic deformation by continuing expansion. When the external force is removed, the inner lining pipe is in plastic deformation and cannot shrink, the outer base pipe is in elastic deformation and tends to shrink, but is limited by the inner lining pipe, and the inner surface of the outer base pipe is forcefully embedded on the outer surface of the inner lining pipe to be compositely formed.

The explosion compounding and hot rolling compounding process is to feed the hollow bimetal composite blank produced with explosion compounding process into annular heating furnace for heating, convey the heated hollow bimetal composite blank to the central line of the perforating machine via roller way and make it pass through the hollow bimetal composite blank into capillary under the action of the roller and the plug of the perforating machine. The hollow billet is moved to a borax station, the inner wall is firstly purged by nitrogen, then borax is sprayed and continuous rolling is carried out, the hollow billet protected by the borax is quickly moved to the center line of the continuous rolling mill, and the hollow billet penetrates into a prepared core rod to be put into a continuous rolling mill together to be rolled into a hollow billet; the continuous rolling pierced billet is conveyed to a stretch reducing center line through a roller way, and is gradually reduced by a stretch reducer to be transformed into the bimetal composite seamless steel pipe.

The preparation process of the five bimetal composite pipes is to compound and form the formed stainless steel pipe and carbon pipe, and the compounded steel pipe has poor roundness, uneven wall thickness and low binding force. The outer base tube and the inner lining tube of the bimetal composite tube prepared by adopting the explosion composite method, the mechanical rolling method, the drawing composite method and the hydraulic composite method have gaps, low production efficiency, small deformation, poor interlayer binding force and small applicable specification range. The explosive cladding and hot rolling cladding method has low production efficiency, high production cost, long production period and small applicable specification range. Meanwhile, in the explosion compounding method and the explosion compounding plus hot rolling compounding method, due to the fact that explosive is needed, certain environmental pollution and potential safety hazards exist. The five production processes have the common defects of low production efficiency, high production cost and small applicable specification range, and limit the popularization and application of the bimetal composite pipe.

The invention aims to overcome the defects in the prior art and provide a preparation method of a bimetal composite pipe. Compared with the existing five preparation modes of the bimetal composite pipe, the preparation method has obvious advantages. The invention overcomes the defects of the traditional composite pipe production method, realizes the full coverage of the composite pipe specification, and has the characteristic of wide coverage of the product specification. The invention overcomes the defects of the traditional composite pipe production method, realizes the interpenetration of the large-deformation rolled composite pipe and the double-layer metal elements, and greatly improves the interlayer binding force and the composite quality. The invention fully plays the characteristics of low cost, low energy consumption, high yield and the like of the outer square tube and the inner round tube, and reduces the cost from the two aspects of technology and raw materials. In addition, the technology of head alignment perforation, rolling control and cooling control and on-line solid solution technology are effectively combined, so that the excellent performance of the bimetal composite pipe under the technology is ensured, the production efficiency of the bimetal composite pipe is greatly improved, the manufacturing cost of the bimetal composite pipe is effectively reduced, and meanwhile, the whole coverage of the production specification set moment of the bimetal composite pipe is realized.

Referring to fig. 1 to 9 in combination, the present invention provides a method for preparing a bimetal composite pipe, comprising the following steps: preparing a tube blank: taking a square tube as an outer layer square tube and a round tube as an inner layer round tube; and (3) assembling: sleeving the outer square tube on the periphery of the inner circular tube, inserting a core rod into the inner circular tube, and inserting an exhaust tube into a gap between the R angle of the outer square tube and the inner circular tube to obtain a fitting tube; pre-heading: pre-heading the assembled pipe to obtain an inner pipe bottle blank and an outer pipe bottle blank with a core rod; periodically rolling a pipe: and (5) performing periodic tube rolling on the inner and outer tube bottle blanks to obtain a composite tube blank.

In this embodiment, the combination between outer side pipe and the inlayer pipe is used, after the periphery of inlayer pipe is established to outer side pipe cover, inlayer pipe and the inner wall of outer side pipe have nearly tangent part, in this part, the clearance between inlayer pipe and the outer side pipe is less, the inlayer pipe moves the shorter distance along the radial, just can contact with outer side pipe, just can produce frictional force between the two, just also can reduce the relative outer side pipe of inlayer pipe to a certain extent and take place the distance of drunkenness, when the minimum clearance between inlayer pipe and the outer side pipe is very little, can also avoid taking place the drunkenness between inlayer pipe and the outer side pipe.

The combination of the outer square tube and the inner circular tube is beneficial to the assembly of the outer square tube and the inner circular tube on one hand; on the other hand, the assembly of the exhaust pipe is facilitated, the gas discharge of the gap between the outer square pipe and the inner circular pipe is facilitated, the quality of the composite pipe blank is ensured, and the interlayer binding force of the composite pipe is greatly improved.

Specifically, according to the model of the bimetal composite pipe prepared as required, corresponding outer square pipe and inner circular pipe are selected, grinding treatment is carried out on the inner and outer surfaces of the outer square pipe and the inner and outer surfaces of the inner circular pipe, surface iron scales and impurities are removed, smoothness of the outer square pipe and the inner circular pipe is guaranteed, and assembly of the outer square pipe and the inner circular pipe is prevented from being influenced due to non-grinding. The metal of the outer square tube is boiler tube grade, heightening tube grade, oil sleeve grade or pipeline tube grade, etc., the metal of the inner round tube is austenitic stainless steel grade, martensitic stainless steel grade, ferritic stainless steel grade or duplex stainless steel grade, and copper base alloy, nickel base alloy, hastelloy, titanium and titanium alloy, etc.

Referring to fig. 1 to 3 in combination, in one embodiment of the present invention, the outer diameter of the inner round tube is 5mm to 10mm smaller than the diameter of the inscribed circle of the outer square tube.

Referring to fig. 1 to 3, in one embodiment of the present invention, the outer square tube has a side length a, a side roughness of 0.2% a or less, a wall thickness of 1.5 to 3 times the corner radius, and a side perpendicularity of 90 ° ± 0.3 °, and the outer diameter of the round tube is 5 to 10mm smaller than the minimum inner diameter of the square tube.

Referring to fig. 1 to 3, in an embodiment of the present invention, in the assembling step, the outer square tube and the inner circular tube of the assembling pipe are axially staggered by a distance of 2 mm-5 mm, so that the tight combination of the covering surfaces during rolling is ensured, and the ends of the inner and outer steel tubes are flush.

In one embodiment, the side length of the outer layer square tube is 192-676 mm, the wall thickness is 36-88 mm, the outer diameter of the inner layer circular tube is 115-490 mm, and the wall thickness is 13.5-90 mm.

Referring to fig. 1 to 4 in combination, in one embodiment of the present invention, the step of performing the pre-heading process includes: the assembly pipe is placed on a heading machine, a first heading module and a second heading module of the heading machine are pressed down, then the first heading module and the second heading module are lifted, the assembly pipe is rotated by 90 degrees, the first heading module and the second heading module are pressed down again, an inner pipe bottle blank and an outer pipe bottle blank are obtained, and vacuumizing and sealing treatment are carried out from an exhaust pipe.

In the step of pre-heading, the hole pattern of the first heading module and the hole pattern of the second heading module are formed by three inclined lines, the sum of the hole pattern widths of the first and second heading modules is 300mm, the first and second heading modules are 218-235 mm in width and 16.8-28 degrees in included angle with the horizontal line, the second and third heading modules are 65-82 mm in width and 6-10 degrees in included angle with the horizontal line, the third and fourth heading modules are 28-145 mm in width and 46-52 degrees in included angle with the horizontal line, the first and second heading modules are 218-235 mm in width and 16.8-28 degrees in included angle with the horizontal line, the second heading module is 65-82 mm in width and 6-10 degrees in included angle with the horizontal line, and the third heading module is 78-32 degrees in included angle with the horizontal line.

Specifically, the first heading module is a left heading module of the heading machine, and the second heading module is a right heading module of the heading machine.

Referring to fig. 1 to 6, in one embodiment of the invention, the outer diameter of a composite pipe blank obtained by periodically rolling a pipe is 150-600 mm, the included angle between the first end of the composite pipe blank and a horizontal line is 46-52 degrees, the included angle between the second end of the composite pipe blank and the horizontal line is 78-83 degrees, and the ratio of the wall thickness of an outer layer square pipe to the wall thickness of an inner layer circular pipe of the composite pipe blank is 1:1.25-6:1, so that the metal cladding of the inner layer and the outer layer of the end is ensured, and the later-stage Zhou Gaduan forming of the composite pipe is facilitated.

Specifically, the first end of the composite tube blank is a left end and corresponds to the first heading module, and the second end of the composite tube blank is a right end and corresponds to the second heading module.

Referring now to fig. 1 to 8 in combination, in one embodiment of the present invention, the steps of periodically rolling a tube include: and (3) periodically rolling the inner and outer tube blanks by using a periodical tube mill group to obtain a composite tube blank, setting the hole pattern of the periodical tube mill group to be phi 150-phi 600mm, determining curve equations of the forging and rolling section, the finishing and rolling section and the blank rolling section by using the hole pattern comprising the forging and rolling section, the finishing and rolling section and the blank rolling section, wherein the forging and rolling section is an envelope curve, the initial angle of the forging and rolling section is 27-30 degrees, the included angle is 74-84 degrees and the curve expansion length is 200-600 mm, and controlling the roller rotating speed of the periodical tube mill group to be 46-72 rpm and the wind pressure to be 3-4 bar.

In the embodiment, the pilger head can be rolled and bent completely through the hole pattern design of the periodically rolled pipe, and the material utilization rate is improved by 20%. The end part of the first end of the inner and outer tube bottle blank is provided with a slope of 28-145 mm, so that periodic endless rolling can be realized.

In one embodiment of the present invention, the step of periodically rolling the tube further comprises the step of heating: preheating the composite tube blank, wherein the preheating temperature is less than or equal to 620 ℃, soaking the composite tube blank, the soaking temperature is 1210-1240 ℃, and the sum of the preheating time and the soaking time is 2.5-16 h.

In this embodiment, the preheating is the temperature of the preheating section when the composite pipe blank enters the annular furnace, and the soaking is the temperature of the soaking section of the composite pipe blank in the annular furnace. The composite pipe blank is heated by the annular furnace, and the stainless steel layer of the composite pipe blank has a plurality of elements and a part of the composite pipe blank has larger specification, so that heating defects and layering are easy to generate, and the proper heating temperature and heating speed in the embodiment are adopted.

Referring to fig. 1 to 7 in combination, in one embodiment of the present invention, the heating step further includes a step of head alignment perforation: and (3) perforating the heated composite tube blank by using a perforating machine to obtain a blank tube, wherein the outer square tube of the blank tube is flush with the tube section of the inner circular tube, the total diameter reduction rate of the perforating machine is 16-18%, the ovality is more than or equal to 0.98 and the expansion rate is 5-20%.

The primary biting and the secondary biting of the composite tube blank are facilitated through the arrangement of the larger total diameter reduction rate; through the arrangement of smaller ellipticity, harmful additional deformation of the capillary tube along the circumferential direction can be reduced, and perforation layering defects of the capillary tube are avoided.

In one embodiment, the ovality is 1.02 to 1.03.

Specifically, the perforator is a cone-type perforator. The outer diameter of the capillary tube is 158 mm-630 mm, and the wall thickness of the capillary tube is 14 mm-110 mm. And designing a flat head plug and a negative plug forward extension perforation process by combining the perforation characteristics of the hollow composite tube blank, wherein the plug forward extension is-10 mm to-20 mm, and the nose part of the plug is arranged at the outlet side of the deformation zone. The ratio of the diameter of the nose of the plug to the diameter of the plug is 0.52-0.75, which is 10-20 mm smaller than the inner diameter of the composite tube blank.

In one embodiment of the present invention, after the step of blind piercing, the method further comprises the step of rolling: rolling the hollow billet to obtain the composite hollow billet.

In this embodiment, rolling is achieved by a mandrel mill, which is a mill for efficiently producing seamless steel pipes, wherein a perforated blank pipe is sleeved on a long mandrel, and the blank pipe is rolled by a plurality of frames arranged in succession, thereby achieving high mechanization and automation. The tube mill group is suitable for producing large-caliber steel tubes, the perforated tube billet is sleeved on the core rod, the tube billet is rolled through Zhou Gagun, the tube rolling step has a deformation mode of forging-rolling joint, a large rolling ratio and excellent comprehensive mechanical properties, so that the tube rolling step is combined, the tube mill pass is designed to be phi 158mm and phi 293mm, the tube mill group pass is designed to be phi 150 mm-phi 600mm, preferably phi 520mm, rolling parameters such as roller spacing, rotating speed and the like are calculated, and the size of the composite pierced billet obtained after rolling is reasonably controlled so as to ensure the physical quality of the incoming materials before sizing.

Specifically, the continuous tube mill designs a continuous roller with high strength and toughness and high heat dissipation, and the weight percentages of chemical elements in the material are as follows: 0.60 to 0.80 percent of C, 0.80 to 1.00 percent of Si, 0.3 to 0.5 percent of Mn, 0.05 to 0.15 percent of Cu, 0.1 to 0.2 percent of Ni, 4.8 to 5.8 percent of Cr, 0.4 to 0.7 percent of Mo, 0.2 to 0.3 percent of W, 0.3 to 0.5 percent of V, 0.0025 to 0.0035 percent of B, 0.08 to 0.15 percent of Al, 0.08 to 0.15 percent of Co, 0.012 to 0.018 percent of N, and the balance of Fe and unavoidable impurities. The tandem mill consists of six frames, and the nominal diameter of the designed tandem mill is 700-720 mm, the width of the mill is 220-240 mm, the eccentricity is 0-3.88 mm, the radius of a connecting arc is 15-50 mm, the radius of a first arc is 323-431 mm, the radius of a mill throat is 117-128 mm, the connecting angle is 8-16.5 degrees, the arc angle of a first hole type is 30-32 mm, the gap between the mill and the mill is 14-16 mm, and the depth of the mill throat is 39.5-45 mm.

In one embodiment of the invention, the step of rolling is followed by the step of reheating: reheating the composite pierced billet by a step furnace, wherein the furnace feeding temperature is lower than 450 ℃, the solid solution strengthening heating temperature of the step furnace is 1000+/-10 ℃, and the heat preservation time is 0.5-4 h.

Referring to fig. 1 to 8 in combination, in one embodiment of the present invention, after the reheating step, the sizing step further includes: and sizing the reheated composite pierced billet by a sizing mill and a cooling water ring on the sizing mill to obtain a composite pipe, and cooling the composite pipe by a cooling water ring group to obtain the bimetal composite pipe. The temperature of the composite pierced billet entering the sizing mill is 940-980 ℃, the temperature of the composite pierced billet exiting the sizing mill is 680-720 ℃, the temperature of cooling water of the cooling water ring set is 670-710 ℃ when the composite pierced billet enters the cooling water ring set, and the temperature of the cooling water ring set is 380-420 ℃ when the composite pierced billet exits the cooling water ring set.

In this embodiment, the sizing mill includes a plurality of pipe roller devices, and a plurality of pipe roller devices set up along the direction of delivery of compound pierced billet, realize combining together with other technologies, and then realize the continuous production of bimetal compound pipe. The sizing frame is provided with a cooling water ring group for quick cooling of the composite pierced billet, namely, after sizing, the composite pierced billet is quickly cooled by a square cooling water ring group, and the included angle between a water ring nozzle of the square cooling water ring group and a vertical line is 10-15 degrees. The total reducing rate of the sizing mill is less than 28%, the reducing rate of the single frame is less than 3%, and the hole type ovality is less than 1.04.

In one embodiment of the invention, the step of reheating and the step of sizing are followed by the step of dephosphorizing with high pressure water: and (3) dephosphorizing the reheated composite pierced billet by using high-pressure water.

In one embodiment of the invention, the sizing step further comprises a cold bed cold cutting step, a head and tail cutting step, a straightening step, a manual inspection step, a nondestructive inspection step, a physical and chemical inspection step, a manual rechecking step and a packaging and warehousing step.

In the embodiment, seven steps after the sizing step are all conventional steps for preparing the bimetal composite steel pipe, so that the quality and the performance of the bimetal composite steel pipe are ensured to meet the requirements.

The invention provides a bimetal composite pipe which is prepared by the preparation method.

In this embodiment, the bimetal composite pipe is manufactured by using all the above manufacturing methods, and has all the technical effects of the bimetal composite pipe, which are not described herein.

Example 1

Preparation of small-caliber bimetal composite pipe

The produced LC2205 stainless steel has the specification of 73mm multiplied by 5.51mm, wherein the specification of the outer square tube is 26CrMo with the specification of 73mm multiplied by 4.51mm, and the specification of the inner circular tube is LC2205 stainless steel with the specification of 63.98mm multiplied by 1mm, and the performance meets the technical requirement of the Q125 steel grade of the oil tube.

Step SA1: preparing a tube blank, namely using the tube blank;

outer square tube: the side length A is 192mm, the wall thickness T is 36mm, the side concave-convex degree is less than or equal to 0.2% A, the corner radius R and the wall thickness T meet R=1.5×T, and the side verticality is not more than 90 degrees+/-0.3 degrees.

Inner layer round tube: the outer diameter is 115mm, the wall thickness is 13.5mm, and the outer diameter of the round pipe is 5mm smaller than the minimum inner diameter of the square pipe.

Step SA2: assembling, namely using the steps of assembling;

the outer square tube and the inner circular tube of the assembly pipe are axially staggered by 2mm.

Step SA3: pre-heading, namely, using the pre-heading;

the first section of the first head-beating module has a width range of 230mm, an included angle with the horizontal line of 16.8 degrees, the second section of the first head-beating module has a width range of 70mm, an included angle with the horizontal line of 6 degrees, the third section of the first head-beating module has a width range of 30.2mm, an included angle with the horizontal line of 50 degrees, the first section of the second head-beating module has a width range of 230mm, an included angle with the horizontal line of 16.8 degrees, the second section of the second head-beating module has a width range of 70mm, an included angle with the horizontal line of 6 degrees, the third section of the second head-beating module has a width range of 6.35mm, and an included angle with the horizontal line of 80 degrees.

Step SA4: periodically rolling the tube, wherein the periodically rolling tube is used;

The hole pattern of the pilger mill group is set to be phi 150mm, the initial angle of the forging section is 27 degrees, the included angle is 74 degrees, the curve expansion length is 300mm, and the roller rotating speed of the pilger mill group is controlled to be 72rpm and the wind pressure is controlled to be 3bar. The end of the first end of the inner and outer tube blanks is provided with a slope of 30 mm.

The outer diameter of the composite tube blank obtained by periodically rolling the tube is 150mm, and the wall thickness is 36mm. The included angle between the first end of the composite tube blank and the horizontal line is 50 degrees, and the included angle between the second end of the composite tube blank and the horizontal line is 80 degrees. The metal of the outer square tube is the oil sleeve mark, and the metal of the inner round tube is the duplex stainless steel mark. The ratio of the wall thickness of the outer square tube to the wall thickness of the inner circular tube of the composite tube blank is 3.5:1.

Step SA5: heating, namely using the heating step;

the preheating temperature is less than or equal to 620 ℃, the composite tube blank is soaked, the soaking temperature is 1210-1240 ℃, and the sum of the preheating time and the soaking time is 2.5h.

Step SA6: a step of head alignment perforation, wherein the head alignment perforation is used;

the total diameter reduction of the piercing mill was 16%, ovality was 1.02, and expansion ratio was 5%. The outer diameter of the capillary obtained by the end-to-end perforation is 158mm, and the wall thickness is 14mm. In the perforating process of the forward extension of the flat head plug and the negative plug, the forward extension of the plug is-10 mm, the nose part of the plug is arranged at the outlet side of the deformation zone, the ratio of the diameter of the nose part of the plug to the diameter of the plug is 0.59, and the diameter of the nose part of the plug is 10mm smaller than the inner diameter of the composite tube blank.

Step SA7: rolling, namely using the rolling step;

the mandrel mill hole is designed to be phi 158mm, and the mandrel mill group hole is designed to be phi 520mm. The high-strength and high-heat-dissipation continuous roller comprises the following chemical elements in percentage by weight: 0.60 to 0.80 percent of C, 0.80 to 1.00 percent of Si, 0.3 to 0.5 percent of Mn, 0.05 to 0.15 percent of Cu, 0.1 to 0.2 percent of Ni, 4.8 to 5.8 percent of Cr, 0.4 to 0.7 percent of Mo, 0.2 to 0.3 percent of W, 0.3 to 0.5 percent of V, 0.0025 to 0.0035 percent of B, 0.08 to 0.15 percent of Al, 0.08 to 0.15 percent of Co, 0.012 to 0.018 percent of N, and the balance of Fe and unavoidable impurities.

Step SA8: reheating, using the reheating step;

step SA9: sizing, namely sizing the steel by using the sizing step;

step SA10: straightening and cutting the head and the tail;

and cutting the head and the tail of the sized bimetal composite pipe by adopting a gang saw, straightening the head and the tail of the bimetal composite pipe by adopting a six-roller straightener, and ensuring the curvature to be not more than 1.2mm/m.

Step SA11: performing manual primary inspection;

and (5) checking the surface quality and the dimensional accuracy of the straightened bimetal composite pipe.

Step SA12: heat treatment;

quenching and tempering, wherein the quenching temperature is 940-970 ℃, the heat preservation time is 18min, the tempering temperature is 640-660 ℃, and the heat preservation time is 36min. The 26CrMo layer obtains a high-strength tempered sorbite structure.

Step SA13: nondestructive flaw detection;

the inner and outer surfaces of the bimetal composite pipe are not allowed to have cracks, folds, scars and separation layers, the L2-level ultrasonic flaw detection is carried out according to the GB/T5777 standard requirement, and the longitudinal and/or transverse defects (defects) of the whole circumference of the pipe body of the bimetal composite pipe can be automatically detected and removed, so that the internal quality of the composite pipe is ensured.

Step SA14: performing physical and chemical inspection;

the bimetallic composite tube performance was tested by sampling and the test performance is shown in table 1.

TABLE 1 mechanical Properties of bimetallic composite tubes

Step SA15: manually rechecking;

the inner surface of the bimetal composite pipe has no defects such as cracks, scratches, indentations, rust and the like which are visible to naked eyes.

Step SA16: packaging and warehousing;

and packaging and warehousing the bimetal composite pipe after spray printing and weighing.

Example two

Preparing a medium-caliber bimetal composite pipe;

the produced specification is 245mm multiplied by 12mm, wherein the specification of the outer square tube is 245mm multiplied by 10mm Q345B, the specification of the inner circular tube is 225mm multiplied by 2mm LC2205 stainless steel, and the performance meets the technical requirements of X70 steel grade pipeline tubes.

Step SA1: preparing a tube blank, namely using the tube blank;

outer square tube: the side length A is 346mm, the wall thickness T is 62mm, the side concave-convex degree is less than or equal to 0.2% A, the corner radius R and the wall thickness T meet R=1.5×T, and the side verticality is not more than 90 degrees+/-0.3 degrees.

Inner layer round tube: the outer diameter is 212mm, the wall thickness is 21mm, and the outer diameter of the round pipe is 10mm smaller than the minimum inner diameter of the square pipe.

Step SA2: assembling, namely using the steps of assembling;

the outer square tube and the inner circular tube of the assembly pipe are axially staggered by 3mm.

Step SA3: pre-heading, namely, using the pre-heading;

the first section of the first head module has a width range of 218mm, an included angle with the horizontal line of 28 degrees, the second section of the first head module has a width range of 82mm, an included angle with the horizontal line of 10 degrees, the third section of the first head module has a width range of 50.3mm, an included angle with the horizontal line of 50 degrees, the first section of the second head module has a width range of 218mm, an included angle with the horizontal line of 28 degrees, the second section of the second head module has a width range of 82mm, an included angle with the horizontal line of 10 degrees, the third section of the second head module has a width range of 10.6mm, and an included angle with the horizontal line of 80 degrees.

the hole pattern of the pilger mill group is set to be phi 280mm, the initial angle of the forging and rolling section is 27 degrees, the included angle is 75 degrees, the curve expansion length is 350mm, and the roller rotating speed of the pilger mill group is controlled to be 62rpm and the wind pressure is controlled to be 3.2bar. The end of the first end of the inner and outer tube blanks was provided with a 50.3mm slope.

The outer diameter of the composite tube blank obtained by periodically rolling the tube is 280mm, and the wall thickness is 60mm. The included angle between the first end of the composite tube blank and the horizontal line is 50 degrees, and the included angle between the second end of the composite tube blank and the horizontal line is 80 degrees. The ratio of the wall thickness of the outer square tube to the wall thickness of the inner circular tube of the composite tube blank is 4:1.

Step SA5: heating, namely using the heating step;

the preheating temperature is less than or equal to 620 ℃, the composite tube blank is soaked, the soaking temperature is 1210-1240 ℃, and the sum of the preheating time and the soaking time is 4 hours.

the total diameter reduction of the piercing mill was 16%, ovality was 1.02, and expansion ratio was 20%. The outer diameter of the capillary obtained by the end-finishing perforation is 336mm, and the wall thickness is 23mm. In the perforating process of the forward extension of the flat head plug and the negative plug, the forward extension of the plug is-15 mm, the nose part of the plug is arranged at the outlet side of the deformation zone, the ratio of the diameter of the nose part of the plug to the diameter of the plug is 0.54, and the diameter of the nose part of the plug is 15mm smaller than the inner diameter of the composite tube blank.

Step SA7: rolling, namely using the rolling step;

the hole pattern of the mandrel mill is designed to be phi 293mm, and the hole pattern of the mandrel mill group is designed to be phi 520mm.

Step SA8: reheating, using the reheating step;

The heat preservation time in the step furnace is 35min.

Step SA9: sizing, namely sizing the steel by using the sizing step;

step SA10: straightening and cutting the head and the tail;

Step SA11: performing manual primary inspection;

Step SA12: nondestructive flaw detection;

the inner and outer surfaces of the bimetal composite pipe are not allowed to have cracks, folds, scars and separation layers, and the L2-level ultrasonic flaw detection is carried out according to the standard requirement of GB/T5777-2019 full circumference automatic ultrasonic detection of longitudinal and/or transverse flaws of seamless and welded (except submerged arc welding) steel pipes, so that the full circumference longitudinal and/or transverse flaws (flaws) of the pipe body of the bimetal composite pipe can be automatically detected, and the pipe body is cleaned, thereby ensuring the internal quality of the composite pipe.

Step SA13: performing physical and chemical inspection;

TABLE 1 mechanical Properties of bimetallic composite tubes

Step SA14: manually rechecking;

Step SA15: packaging and warehousing;

Example III

Preparation of heavy caliber bimetal composite pipe

The produced specification is 508mm multiplied by 75mm, wherein the specification of the outer square tube is 508mm multiplied by 40mm 20G, the specification of the inner round tube is 428mm multiplied by 35mm TP304L, and the performance meets the technical requirements of a 20G high-pressure boiler tube.

Step SA1: preparing a tube blank, namely using the tube blank;

outer square tube: the side length A is 676mm, the wall thickness T is 88mm, the side concave-convex degree is less than or equal to 0.2 percent A, the corner radius R and the wall thickness T meet R=3×T, and the side verticality is not more than 90 degrees+/-0.3 degrees.

Inner layer round tube: the outer diameter is 490mm, the wall thickness is 90mm, and the outer diameter of the round pipe is 10mm smaller than the minimum inner diameter of the square pipe.

Step SA2: assembling, namely using the steps of assembling;

the outer square tube and the inner circular tube of the assembly pipe are axially staggered by 5mm.

Step SA3: pre-heading, namely, using the pre-heading;

the first section width range of the first heading module is 235mm, the included angle between the first section width range of the first heading module and the horizontal line is 28 degrees, the second section width range of the first heading module is 65mm, the included angle between the second section width range of the first heading module and the horizontal line is 10 degrees, the third section width range of the first heading module is 125.9mm, the included angle between the third section width range of the first heading module and the horizontal line is 50 degrees, the first section width range of the second heading module is 235mm, the included angle between the first section width range of the second heading module and the horizontal line is 28 degrees, the second section width range of the second heading module is 65mm, the included angle between the second section width range of the second heading module and the horizontal line is 10 degrees, the third section width range of the second heading module is 26.5mm, and the included angle between the third section width range of the second heading module and the horizontal line is 80 degrees.

the hole pattern of the pilger mill group is set to be phi 600mm, the initial angle of the forging section is 30 degrees, the included angle is 84 degrees, the curve expansion length is 600mm, and the roller rotating speed of the pilger mill group is controlled to be 46rpm and the wind pressure is controlled to be 4bar. The end of the first end of the inner and outer tube blanks was provided with a 125.9mm slope.

The outer diameter of the composite tube blank obtained by periodically rolling the tube is 600mm, and the wall thickness is 150mm. The included angle between the first end of the composite tube blank and the horizontal line is 50 degrees, and the included angle between the second end of the composite tube blank and the horizontal line is 80 degrees. The ratio of the wall thickness of the outer square tube to the wall thickness of the inner circular tube of the composite tube blank is 1:1.03.

Step SA5: heating, namely using the heating step;

the preheating temperature is less than or equal to 620 ℃, the composite tube blank is soaked, the soaking temperature is 1210-1240 ℃, and the sum of the preheating time and the soaking time is 16h.

the total diameter reduction of the piercing mill was 16%, ovality was 1.02, and expansion ratio was 5%. The outer diameter of the capillary obtained by the end-finishing perforation is 630mm, and the wall thickness is 110mm. In the perforating process of the forward extension of the flat head plug and the negative plug, the forward extension of the plug is-20 mm, the nose part of the plug is arranged at the outlet side of the deformation zone, the ratio of the diameter of the nose part of the plug to the diameter of the plug is 0.74, and the diameter of the nose part of the plug is 20mm smaller than the inner diameter of the composite tube blank.

Step SA7: rolling, namely using the rolling step;

the hole pattern of the pilger mill group is designed to be phi 520mm. The high-strength and high-heat-dissipation continuous roller comprises the following chemical elements in percentage by weight: 0.60 to 0.80 percent of C, 0.80 to 1.00 percent of Si, 0.3 to 0.5 percent of Mn, 0.05 to 0.15 percent of Cu, 0.1 to 0.2 percent of Ni, 4.8 to 5.8 percent of Cr, 0.4 to 0.7 percent of Mo, 0.2 to 0.3 percent of W, 0.3 to 0.5 percent of V, 0.0025 to 0.0035 percent of B, 0.08 to 0.15 percent of Al, 0.08 to 0.15 percent of Co, 0.012 to 0.018 percent of N, and the balance of Fe and unavoidable impurities.

Step SA8: straightening and cutting the head and the tail;

Step SA9: performing manual primary inspection;

Step SA10: heat treatment;

solid solution + normalizing: solid solution temperature: heat preservation time is 80min at 1060-1070 ℃, normalizing temperature: the temperature is 910 ℃ to 930 ℃ and the heat preservation time is 100min.

Step SA11: nondestructive flaw detection;

Step SA12: performing physical and chemical inspection;

TABLE 1 mechanical Properties of bimetallic composite tubes

Step SA13: manually rechecking;

Step SA14: packaging and warehousing;

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects: the inner layer round tube is sleeved on the outer periphery of the inner layer round tube, the inner wall of the inner layer round tube and the inner wall of the outer layer round tube are provided with a nearly tangent part, in the part, the gap between the inner layer round tube and the outer layer round tube is smaller, the inner layer round tube moves along the radial direction by a shorter distance, the inner layer round tube can be in contact with the outer layer round tube, friction force can be generated between the inner layer round tube and the outer layer round tube, the moving distance of the inner layer round tube relative to the outer layer round tube can be reduced to a certain extent, and when the minimum gap between the inner layer round tube and the outer layer round tube is very small, the moving between the inner layer round tube and the outer layer round tube can be avoided.

It will be apparent that the embodiments described above are merely some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The preparation method of the bimetal composite pipe is characterized by comprising the following steps of:

preparing a tube blank: taking a square tube as an outer layer square tube and a round tube as an inner layer round tube;

and (3) assembling: sleeving the outer square tube on the periphery of the inner circular tube, inserting a core rod into the inner circular tube, and inserting an exhaust tube into a gap between the R angle of the outer square tube and the inner circular tube to obtain a fitting tube;

Pre-heading: pre-heading treatment is carried out on the assembled pipe to obtain an inner pipe bottle blank and an outer pipe bottle blank with a core rod;

periodically rolling a pipe: and (5) performing periodic tube rolling on the inner and outer tube bottle blanks to obtain a composite tube blank.

2. The method for producing a bimetal composite pipe according to claim 1, wherein the outer diameter of the inner round pipe is 5mm to 10mm smaller than the diameter of the inscribed circle of the outer square pipe.

3. The method for producing a bimetal composite pipe according to claim 1, wherein the side length of the outer square pipe is a, the side concavo-convex degree is less than or equal to 0.2% a, the corner radius is 1.5-3 times the wall thickness, and the side verticality is 90 ° ± 0.3 °, and the outer diameter of the round pipe is 5-10 mm smaller than the minimum inner diameter of the square pipe.

4. The method for manufacturing a bimetal composite pipe according to claim 1, wherein in the step of assembling, the outer square pipe and the inner circular pipe of the assembled pipe are axially staggered by a distance of 2mm to 5 mm.

5. The method of manufacturing a bimetal composite pipe according to claim 1, wherein in the step of pre-heading, the step of performing the pre-heading process includes: placing the assembly pipe on a heading machine, pressing down a first heading module and a second heading module of the heading machine, then lifting up the first heading module and the second heading module, rotating the assembly pipe by 90 degrees, pressing down the first heading module and the second heading module again to obtain an inner pipe bottle blank and an outer pipe bottle blank, and carrying out vacuumizing and sealing treatment from the exhaust pipe.

6. The method according to claim 5, wherein in the pre-heading step, the hole pattern of the first heading module and the hole pattern of the second heading module are both formed by three oblique lines, the sum of the hole pattern widths of the first and second heading modules is 300mm, the first section width of the first heading module ranges from 218mm to 235mm, the included angle with the horizontal line is 16.8 ° to 28 °, the second section width of the first heading module ranges from 65mm to 82mm, the included angle with the horizontal line is 6 ° to 10 °, the third section width of the first heading module ranges from 28mm to 145mm, the included angle with the horizontal line is 46 ° to 52 °, the first section width of the second heading module ranges from 218mm to 235mm, the included angle with the horizontal line is 16.8 ° to 28 °, the second heading module ranges from 65 ° to 82 ° and the included angle with the horizontal line is 4 ° to 32 °.

7. The method for producing a bimetal composite pipe according to any one of claims 1 to 6, wherein the outer diameter of the composite pipe blank obtained by the periodic pipe rolling is 150mm to 600mm, the included angle between the first end of the composite pipe blank and the horizontal line is 46 ° to 52 °, the included angle between the second end of the composite pipe blank and the horizontal line is 78 ° to 83 °, and the ratio of the wall thickness of the outer square pipe to the wall thickness of the inner circular pipe of the composite pipe blank is 1:1.25 to 6:1.

8. The method of preparing a bimetallic composite tube as set forth in claim 7, wherein the step of periodically rolling the tube comprises: and (3) periodically rolling the inner and outer tube blanks by using a periodical tube rolling mill group to obtain a composite tube blank, setting the hole pattern of the periodical tube rolling mill group to be phi 150-phi 600mm, wherein the hole pattern comprises a forging rolling section, a finish rolling section and an idle rolling section, determining curve equations of the forging rolling section, the finish rolling section and the idle rolling section, wherein the forging rolling section is an envelope curve, the initial angle of the forging rolling section is 27-30 degrees, the included angle is 74-84 degrees, the curve expansion length is 200-600 mm, and controlling the roller rotating speed of the periodical tube rolling mill group to be 46-72 rpm and the wind pressure to be 3-4 bar.

9. The method of producing a bimetallic composite tube according to any one of claims 1 to 6, further comprising the step of heating after the step of periodically rolling the tube: preheating the composite tube blank, wherein the preheating temperature is less than or equal to 620 ℃, soaking the composite tube blank, the soaking temperature is 1210-1240 ℃, and the sum of the preheating time and the soaking time is 2.5-16 h.

10. The method of preparing a bimetallic composite tube of claim 9, further comprising the step of flush perforating after the step of heating: and perforating the heated composite tube blank by using a perforating machine to obtain a blank tube, wherein the outer square tube and the inner circular tube of the blank tube are flush, the total diameter reduction rate of the perforating machine is 16% -18%, the ovality is 1.02 and the expanding rate is 5% -20%.

11. The method of preparing a bimetallic composite tube according to claim 10, further comprising the step of rolling after the step of butt perforating: and rolling the hollow billet to obtain the composite pierced billet.

12. The method of preparing a bimetallic composite tube of claim 11, wherein the step of rolling is followed by the step of reheating: and reheating the composite pierced billet by a stepping furnace, wherein the furnace feeding temperature is lower than 450 ℃, the solid solution strengthening heating temperature of the stepping furnace is 1000+/-10 ℃, and the heat preservation time is 0.5-4 h.

13. The method of preparing a bimetallic composite tube of claim 12, wherein the step of reheating is followed by the step of sizing: sizing the reheated composite pierced billet by a sizing mill and a cooling water ring on the sizing mill to obtain a composite pipe, cooling the composite pipe by a cooling water ring group to obtain a bimetal composite pipe, wherein the temperature of the composite pierced billet entering the sizing mill is 940-980 ℃, the temperature of the composite pierced billet exiting the sizing mill is 680-720 ℃, the temperature of cooling water of the cooling water ring group is 670-710 ℃ when the composite pierced billet enters the cooling water ring group, and the temperature of cooling water of the cooling water ring group is 380-420 ℃ when the composite pierced billet exits the cooling water ring group.

14. A bimetallic composite tube produced using the production method of any one of claims 1 to 13.